Effects of recording-erasure dynamics of storage capacity of a wavelength-multiplexed reflection-type photorefractive hologram

Interleaving and error correction in volume holographic memory systems

We study the use of error-correction coding (ECC) and two-dimensional interleaving for volume holographic memory (VHM) systems suffering from both random and systematic errors. The bit-error rate (BER) is used as the data-fidelity measure and as a design metric for optical 4f systems. The correlated error patterns arising from both lens aberrations and misalignment errors are analyzed, and we discuss the information theoretic storage capacity of VHM in the presence of such correlated error patterns. The performance of interleaving and ECC is analyzed from both BER and storage-capacity perspectives. Magnification, rotation, tilt, and defocus errors are also studied, and an experimental demonstration that combines ECC with two-dimensional interleaving is included.

Off-Bragg analysis of the diffraction efficiency of reflection photorefractive holograms

Formulas are given for the calculation of diffraction efficiency of reflection-type gratings recorded in a photorefractive medium. The analysis incorporates the coupled-wave theory that was developed for photorefractive hologram gratings. This analysis takes into account grating slant with respect to the medium surface, light absorption during reconstruction, any incident angle of the reference beam, and any photorefractive phase shift. General solutions for signal and reference wave functions are given in a closed-form expression by use of a hypergeometric function. The optimum media parameters and recording conditions for high diffraction efficiency are obtained by the derived formulas. The diffraction properties for off-Bragg conditions are also discussed.

Wavelength-multiplexed holographic data storage by use of reflection geometry with a cerium-doped strontium barium niobate single-crystal structure and a tunable laser diode

We present wavelength-multiplexed holographic recording forhigh-density, high-speed data storage using reflection geometry with ahigh-sensitivity cerium-doped strontium barium niobate single-crystalstructure and second-harmonic generated light from a compact andconvenient wavelength-tunable laser diode. We have recorded andreconstructed wavelength-multiplexed holograms by using wavelengths0.053-nm apart. The theoretical wavelength selectivity of thehologram with the linewidth of the light source taken intoconsideration agrees well with the experimental wavelength selectivity.

Combination of free-space and guided-wave optical interconnects for angularly multiplexed multiwavelength holographic memory

We propose and test experimentally a new scheme to implement spatially multiplexed multiwavelength holographic memory. An electro-optically modulated phase grating array on LiNbO(3) substrate is used as a guided-wave interconnect to activate the reconfigurable reference beam. The object beam is provided by free-space interconnect. An electro-optic modulation efficiency of 18 +/- 2.5% is achieved with an applied voltage of 100 V. The reference beams with different diffraction angles can implement the angle-multiplexing holographic recording. We believe this is the first report of the implementation of guided-wave electro-optic interconnect together with free-space interconnect in holographic memory applications.

Off-Bragg analysis of the diffraction efficiency of transmission photorefractive holograms

Formulas for calculating the diffraction efficiency of gratings recorded in a photorefractive medium are given. The analysis uses coupled-wave theory for photorefractive hologram gratings and takes into account the photorefractive phase shift and fringe-bending effect. General solutions for diffracted (signal) and undiffracted (reference) waves are derived in a closed-form expression. By use of the derived formulas the diffraction efficiency for angle mismatch from the Bragg condition can easily be evaluated as compared with numerical-analysis methods. The diffraction efficiency is also quantified in terms of medium parameters and recording and reconstruction conditions.

Sparse-wavelength angle-multiplexed volume holographic memory system: analysis and advances

We present and analyze our hybrid wavelength-and-angle-multiplexed volume holographic memory system. The hybridization of wavelength and angle multiplexing relaxes demands on spectral-tuning sources, angle-tuning devices, and optical system numerical apertures while maintaining a large K-space addressability. We consider realistic properties of our volume holographic memory system, addressing practical issues such as storage density and material-dependent photon-limited information throughput. Finally, we present experimental results of the storage of 2000 sparse-wavelength angle-multiplexed volume holograms in a 1.86-cm3 volume of lithium niobate.